Methods and apparatus for particle beam dose profile measurement

Abstract

Examples of the present disclosure relate to a particle beam dose profile measurement apparatus comprising a particle detector stack comprising a plurality of scintillator layers. Each scintillator layer of the detector stack is disposed along an axis of the apparatus such that the axis projects through each layer. Each scintillator layer is configured to produce scintillation light indicative of an energy deposition, in that scintillator, of a particle beam incident upon the detector stack along said axis. The apparatus comprises readout circuitry configured to measure the scintillation light of each scintillator layer; and dose profile determination circuitry configured to determine a dose profile of said particle beam within the detector stack. Said determining is based on the measured scintillation light of each scintillator layer, and a quenching correction.

The invention claimed is: 
     
       1. A particle beam dose profile measurement apparatus comprising:
 a particle detector stack comprising a plurality of scintillator layers, wherein:
 each scintillator layer of the detector stack is disposed along an axis of the apparatus such that the axis projects through each layer; and 
 each scintillator layer is configured to produce scintillation light indicative of an energy deposition, in that scintillator, of a particle beam incident upon the detector stack along said axis, 
 
 readout circuitry configured to measure the scintillation light of each scintillator layer; and 
 dose profile determination circuitry configured to determine a dose profile of said particle beam within the detector stack, said determination is based on:
 fitting a theoretical energy deposition profile to the measured scintillation light of each scintillator layer, 
 wherein said theoretical energy deposition profile comprises a quenching correction. 
 
 
     
     
       2. The apparatus of  claim 1 , wherein the theoretical energy deposition profile is based on a Bragg curve modified by said quenching correction. 
     
     
       3. The apparatus of  claim 2 , wherein the Bragg curve is based on Bortfeld's analytical approximation. 
     
     
       4. The apparatus of  claim 1 , wherein the quenching correction is based on Birks' law. 
     
     
       5. The apparatus of  claim 1 , wherein the determining the dose profile of the particle beam within the particle detector stack comprises:
 based on the measured scintillation light of each scintillator layer, determining an emitted light profile of the particle beam along said axis within the particle detector stack; and 
 applying the quenching correction to the determined emitted light profile of the particle beam, to determine the dose profile. 
 
     
     
       6. The apparatus of  claim 1 , wherein the readout circuitry comprises, for each scintillation layer of the particle detector stack, at least one photodiode configured to receive the scintillation light of that scintillator layer. 
     
     
       7. The apparatus of  claim 1 , wherein the dose profile determination circuitry comprises dedicated circuitry configured to:
 receive, from the readout circuitry, an indication of the measured scintillation light of each scintillator layer; and 
 output an indication of the determined dose profile. 
 
     
     
       8. The apparatus of  claim 7 , wherein the dedicated circuitry is a field-programmable gate array. 
     
     
       9. The apparatus of  claim 1 , wherein each scintillator layer comprises a plastic scintillator. 
     
     
       10. The apparatus of  claim 1 , wherein each scintillator layer has a transverse size at least as large as an expected scanning field of the particle beam. 
     
     
       11. The apparatus of  claim 1 , wherein the particle beam is a therapeutic particle beam. 
     
     
       12. The apparatus of  claim 1 , wherein the particle beam is a proton beam. 
     
     
       13. The apparatus of  claim 1 , wherein the dose profile is a longitudinal energy deposition profile. 
     
     
       14. The apparatus of  claim 1 , wherein each scintillator layer has a density substantially equal to a density of water. 
     
     
       15. A method for determining a dose profile of a particle beam, the method comprising:
 receiving the particle beam at a particle detector stack comprising a plurality of scintillator layers, the particle beam being parallel to a longitudinal axis of the particle detector stack; 
 measuring scintillation light of each scintillator layer of the particle detector stack; and 
 determining a dose profile of said particle beam within said particle detector stack, said determining being based on:
 fitting a theoretical energy deposition profile to the measured scintillation light of each scintillator layer, 
 wherein said theoretical energy deposition profile comprises a quenching correction. 
 
 
     
     
       16. A method according to  claim 15 , comprising:
 based on the determined dose profile, determining at least one of:
 a range of the particle beam within the particle detector stack; 
 a depth of an energy deposition peak within the particle detector stack; 
 a width of the energy deposition peak of the particle beam within the particle detector stack; and 
 a water equivalent path length of the particle beam within the particle detector stack. 
 
 
     
     
       17. A method according to  claim 15 , comprising determining the dose profile for at least one predetermined particle beam energy. 
     
     
       18. A computer readable medium comprising computer-readable instructions which, when executed by at least one processor, cause the at least one processor to perform a method of determining a dose profile of a particle beam, the method comprising:
 receiving the particle beam at a particle detector stack comprising a plurality of scintillator layers, the particle beam being parallel to a longitudinal axis of the particle detector stack; 
 measuring output light of each scintillator layer of the particle detector stack; and 
 determining a dose profile of said particle beam within said particle detector stack, said determining being based on:
 fitting a theoretical energy deposition profile to the measured output light of each scintillator layer, 
 wherein said theoretical energy deposition profile comprises a quenching correction.